Cooling woes...what can I do better?
 

Mods:
New Koyo Radiator
New Factory Radiator Caps (13 psi)
New Factory Thermostat (Full open at 95C)
New Factory Radiator Hoses
New Factory Ducting in place (lower foam installed)
Single 34 row earls oil cooler with -10AN lines (my drivers side one is damaged & bypassed until I change it this weekend)
Autometer oil temp gauge (sensor at oil filter)
Autometer water temp gauge (sensor at T-Stat outlet)
Freshly evaculated and serviced AC system (R-12 fill)
Newly Installed Power FC

Coolant Combo:
84.4% Distilled water
12.5% Prestone Green Antifreeze
3.1% Redline Water Wetter (that's spec)

It's been 104-105F here the last couple days. I was seeing 225-230F coolant temps on my Autometer gauge...freightening. I installed my PowerFC today to turn the fans on earlier. I tested the fans by setting them to come on at 80C and they were blasting away. Cruising with the A/C off in 101F-95F ambient temps I recorded 93-95C (199-203F) coolant temps on the PowerFC (and the Autometer agreed). Well...that's OK I guess for the ambient temp. Turn on the A/C and coolant temps started creeping up to 100C (212F) then went up pretty quickly to 104C (219F) when I got into traffic. After I got out of traffic and was cruising at 49-54 mph it just stayed at 104C (219F) and refused to move. Both fans were still on max. Oil temps were constantly 15-19F under coolant temps.

A few things
- It uses no coolant
- No bubbling in the AST or filler
- Theres a hair bit of brown particular matter under the fill cap. I don't think that's a problem though.

For more background I just completed a 1600 mile round trip up to Salt Lake City and back with the car. Water temps were 179F-207F the whole time depending on load (lotsa hill climbs), ambient temps, and A/C usage. On the way home going thru Phoenix it was 95F and I saw a peak of 210F (99C) while cruisng at 64 mph with the AC on. When it was cool out (<80F) the thing just stuck at 181-185F the whole time with the A/C on (or off) at any speed up to 84 MPH.

I can see how you guys that live in average climates could be running 85C or less. I'd like to see you try 100-105F on for size...I don't think you'd be so quick to yell "victory!" like the norm around here.

So anyway...I've got some things on my mind. Installing some aluminum sheets to the radiator endtanks to seal off the sides of the radiator. I don't think that's going to do much for my problem though....maybe 1-2F. A vented hood. Something like the knight sports model. I'm not sure how much that will do for me. Problem is I'm strapped for cash now so that will have to wait. The other thing on the plate is 4 gallons of Evans NPG-R coolant that are sitting downstairs waiting to be installed. I've run NPG+ before in my Stealth. It brought coolant temps up (some) but there was absolutely no chance of boiling over. With better ducting and good oil cooling I was able to dump the Evans and the car is fine now on conventional coolant. Too bad the seven won't cooperate like that.

Is there anything else you guys see that I can do better? I'm avoiding the NPG-R but it's looking like that's my last option. The peak summer temps are still about a week or two away so I need to get this resolved....or at least minimalized.

It sounds like you have done everything right. 225 degree coolant temps, although high, are not in the danger zone. Just be sure you take it easy when the temps are hot, and you will be fine. Setting your fans to come on at a lower temp is a good idea.

Radiator ducting isn't going to help when you are drivng slow, which is your main problem area.

not trying to hijack the tread, but i'm having a similar issue right now (i don't have all the mods and its not "quite" as hot here as that, it was about 98F ambient here for the last two or three days. my problem turned out to be that one of my cooling fans (the passanger side one which is MUCH more difficult to see with the battery in stock location and an SMIC with a duct blocking most of the viewable area of the fan) stopped working... the electric motor had done this to me before. It needed to be taken apart, cleaned, and repacked with grease. Eventually (Fall) i'm going to just buy a new one when i have a little upkeep done on my car but for now, its going back to the shop to get repacked.

long story short, be absolutely positive that both of your fans are working not just "think" that they are working. if it is 100F here and i have my A/C on and everything is running as it should, i see 95C all day, but that's as high as it gets.

many people have said that the coolant temps parallel what the oil temps are doing. Can you explain what happened or how you have the drivers side oil cooler bypassed?

sealing the sides of the radiator is a big improvement, it's next on my list of mods. search for damian's posts about it

If you didn't seal the sides of the rad with foam (like oem) or aluminum, you just reduced your cooling capacity. On hiway, this provides a bypass for air vs going through the thick koyo and ac core. In traffic, hot air exiting the fans will loop back by the sides of the rad, and recirc through the cores, with less new "cool" going into the bumper opening.

Fix this 1st. Pressure test system (tee at ast). You should have better performance than you did before.

Whatever was done to make the system run hotter must be fixed, before considering NPG+.

Correct - NPG has less heat capacity, so it will make the coolant run even hotter!

Roger...Wilco. Good ideas guys.

I'm not sbsolutely certain that both fans are operating but I can hear the difference between the fans when the A/C is on and they're barely on and when the power FC kicks everything up to high. It's quite loud...I can't see that being just one fan. Regardless though I will pull the intake box and ops check both fans visually to ensure they're on.

My oil temps are under coolant temps because I have upgraded oil coolers. Two 34 row Earls coolers. One of them is damaged (an R1 lip nutplate chaffed a hole in it) so its bypassed with a -10AN union until I replace it this weekend. Even on one cooler though I still run sub 185-200F oil temps when the coolant is pushing upwards of 220F.

I didn't make the connection that sealing the sides of the radiator would make such a big difference. So now that you mention that when feeling in the front bumper for airflow with the fans on max I feel air moving/swirling (its not linear towards the radiator) and its much warmer than ambient. I think you guys may be correct about the fans recirculating already heated air.

I know all about the NPG's specific heat. That's why I'm avoiding it until I've exhausted all other options.

One more thing to throw out there...the new revision ?96 or 99? fans. Are they direct bolt ons? Do they move more air?

I changed over to the 99 fans. They are not bolt ons. The inner diameter is larger that the stock one. You need to make a little shim for it to fit.

https://www.rx7club.com/forum/showth...highlight=shim

Honestly, it "feels" like they move more air but I could easily be mistaken. I recently switched over to Evans as my car actually runs too cold. With the PFC set to have the fans come on at 91 degrees C, the temp will hold there for me even in stop and go traffic (limited) in texas heat.

Althought you know what you are doing,i have to ask:do you have the underbelly pan installed?

Yep...the underbody is on there. It wasn't when I picked the car up from Chicago though. I had to buy a new one from Malloy.

I'm having similar problems as you.

Do you have a FMIC or SMIC?

I have a blitz FMIC and my radiator sits quite far back in my engine bay. I don't think enough fresh air is getting back to it. I used to have it ducted so that the center section of the radiator was sealed against the IC and the condensor. I have since removed some of the ducting to promote more fresh air to the radiator with some sucess.

I have a mazdaspeed replica hood and honestly, I'm kinda dissapointed on how hot my engine bay gets. I may need to make some ducting to pull air out.


I have a fairly new radiator, both fans work and a vented hood and I still have creeping temps. Once I get on the highway, things stay fairly cool though. (200F w A/C on, <190F w/o A/C)

Has anyone had good luck with Royal Purple Purple Ice?

Run a higher pressure cap 19 psi as the car was originally designed to run with 19-21 psi. This will give you some headroom till boilover. Shut the car off after a hot run; wait 15 minutes and watch your gauge go up to 280F, hence the gurgling noise.

The brown crud, I would watch that carefully.

Meh, this topic's depressing, do other turbo'd vehicles ever have this problem (Spare me the LS1 posts...)? Never had to worry with My Mr2-Turbo....Supras?

I hope its something simple, that 13psi vs. 19psi Cap someone just brought up changes a great deal on how the coolant works if I am not mistaken, it's all about pressure....

I'm on the stock SMIC until my backordered ASP Medium gets here.

I'm all for the 19 psi cap. Matter of fact I run a 21.3 psi cap on my Stealth for the same reason. The thing that kept me from getting even a 16 psi cap is that Mazda actually changed from a 16 psi down to a 13 psi right? Whats the reasoning? I seem to remember rumblings that it was the coolant seals...is that correct? I mean the service manual has you pressure check the system up to 20.6 psi so its not that crazy. I'm still leary of anything over 13 psi though.

3000GTs & Stealths don't normally have cooling problems unless something actually fails or you install a FMIC without any ducting. Things get ugly without ducting.

whats the lbs on the ast cap? I upgraded mine to a 22-25lbs cap and the temps went down a bit

Wow...now that's a testimonial if I ever heard one. 22psi? Geeze! 19 should be no problem then...hmmm.

yeah, mine is really loud too but if you've only listened to it with one fan running, you'd never know the difference... hell, i've heard both and still couldn't figure it out without looking at the fans themselves when they were supposed to be on.

i highly recommend sealing the sides of your radiator and checking those fans out, be careful when examining the driver's side fan (which i just realized is the one i have issues with, not the passanger) it can look like its moving if the fan blade stops in the right place and actually not be moving at all (this is only an issue if you look at it without removing the IC duct).

good luck

p.s. if you DO end up needing a new fan motor, i just priced them out from Malloy Mazda and its $203ea.

Oh...forgot to post. I watched both fans operating yesterday while working the idle with the Power FC. They're fine.

I'm going to tear into the car tomorrow morn to seal off the sides of the rad and replace my holy driver's side oil cooler.

Yup! That and blowing hoses (turbo-coolant, for example).

A worn water pump will also make it run hotter.

I did some mods today.

- Sealed off the forward most open areas on the sides of the stock underbody tray
- Sealed off the drivers side of the radiator
- Installed an SR Motorsports air box (which semi-seals off the passenger side of the radiator and draws air from there)
- Installed the upper Bomex intake pipe (the lower is impossible to install with this airbox)

The new airbox leaves a little bit of open area next to the SMIC. Defintely helps the passenger side fan move some air out of the radiator.

Coolant temps droped down to 88C (190F) but my autometer temp gauge showed 194F. Once I turned on the A/C it went up to 100C (212F) and once I started beating on the car hard it hit 101C (214F) and wouldn't go up any more from there. The Autometer pretty much agreed with the PowerFC. Ambient temp was 101F, I was cruising at 55mph or less with occasional stoplights, I'm still on one 34 row oil cooler, and fans come on max at 95C.

That's better...still not great though.

I'm thinking about a 16 psi AST cap. I'd like to install a vented hood too but I don't have the mooola.

I don't know...I think its getting to be NPG-R time. There not much left to do besides those two things and replacing that drivers side oil cooler. The thing is low oil temps don't seem to drag down coolant temps near as much as they do in a piston motor.

flush your system and use evans ngp+ waterless coolant

Says the guy from Canada. ;)




I thought my cooling system was great until I moved to where it gets really hot...:)

That sounds pretty good to me, especially with the Arizona heat. I wouldn't worry about it if you aren't seeing temps above 220F... heck, the stock ECU doesn't even turn the fans on until 226F!

BTW, how much was the undertray from Malloy?

where is your aftermarket gauge for the autometer located? i ask because if its up top next to the coolant cap, it can sometimes grab an arch of electricity and give you a wrong read. loosening the cap ever so slighty can remedy this, by that i mean less than a 32nd so as to not lose your coolant pressure.

you .2% off..... ;) hahahha j/k

I mean...yeah...I guess 214F isn't bad. I don't think I would call it good either. I doubt it would be able to handle a road course either.

The undertray was like ?$158? and ray had to charge me somewhere around $30 shipping since its oversized.

The Autometer water temp sensor is in the filler neck right forward of the thermostat...about as low as I could go on the filler neck.

I installed a 16psi radiator cap for a little extra boil over protection. It's harder on the coolant system but I think its worth it while running conventional coolant. No leaks (yet).

I also replaced that holy 34 row oil cooler so I'm working with a pair of them again. Oil temps were 150-170F the whole time.

100F ambient and the fans set to come on at 95C (203F)

No AC - 92-95C (195-203F)
A/C - 96-97C (205-207F)
A/C after 0-100 mph blast - 99C (210F) peak
No A/C again - 92-95C (195-203F)

That's much improved. I've got no worries about daily driving it with the A/C on right now. I wouldn't want to try to road course the car in these ambient temps though.

The real test will be later this week...they're forecasting a high of 110F for Thursday. I don't think it'll be a problem. ;)

After this week I'll probably make the switch over to NPG-R. We'll see though.

BTW...the stock IC sucks...66-78C (151-172F) air temps. Blah!

I had similiar temps. with me car but was easy to pinpiont the problem.
Autometer gauge 220-230f
PFC 190f (88c)
I just figured the guage is junk....try a new or better guage

Unless you are reading the temp from the same location (i.e. both sensor fairly close to each other), you aren't really comparing apples to apples.

Says the guy from Canada :) (all in fun there! ;) )

My Autometer gauge and my PowerFC usually agree. About the only time they differ is when the PowerFC lags behind. The Autometer responds to changes much quicker. That being said all the temps in my above post are off the PowerFC (since that's what most people compare).

The temps may sound abnormally high to you but you have to understand that even (what sounds like) a small increase from 80F to 100+F will reveal practically every problem with your cooling system. The requirements go up rather quickly...especially in stop and go traffic. Alot of you guys in cooler climates that think you have your cooling system perfected would probably be surprised at your coolant temps if you were forced to daily drive in a location that topped 100F daily.

So...yeah after a few trips home in 104F weather and seeing 103C (217F) and hearing boiling after shutting off the car I'm definitely switching to NPG-R this coming weekend.

In the meantime I decided to do a little experiment. I pumped out 0.6 gallons of my 12.5% coolant mix and poured in straight conventional antifreeze to bring the mix up to 35% (the minimum the service manual reccomends). Well...bad idea. On the way to work this morning (80F) temps were slightly elevated from yesterday with the A/C off. On the way home from work (105F ambient & A/C blastin) I watched the PFC climb to 106C (223F) and sit there. As I said...I saw a peak of 103C (217F) yesterday in 104F ambient temps on the same drive.

Yep...that didn't work. ;)

don't be surprised if you see higher temps with the evans.

Nah...I won't be. I fully expect it to run a little hotter in all but the coolest conditions.

I won't be a slave to the coolant temp any longer though. ;) I won't have to worry about oil temp with the dual 34-row RE cooler setup either.

Anyone know if the A/C shuts of automatically at a certain coolant temp? Going thru the service manual I saw reference to a thermoswitch that switches at 115C (239F) coolant temp then switches back once coolant temp drops back below 110C (230F). It didn't say what it controls though. I wonder if that's it. I also wonder if that auto-shut-off will still operate with the Power FC installed.

I doubt I'll see 115C just tooling around town but I'm curious.

Sooo...yesterday I drained the block & radiator and sucked all of the old coolant out of the overflow. I filled it up with 100% antifreeze to absorb all the water in preperation for the NPG-R. Turned off the fans with the Power FC and let it heat up to 115C at idle with the radiator cap off & heater on to attempt to boil out what water was left in the system. Took it for a spin with the cap back on (no undertray) and it ran about 106C (no fans) in 100F ambient. Then I let it cool for a few hours, topped it off with more antifreeze, and let it sit over night.

This morning I used some foam from a local textile place and closed up the last holes I could find. Worked out great. I swapped out yesterday's 100% antifreeze for Evans NPG-R. If you haven't read about it yet it's mostly Etheylene Glycol based (Vs Propylene Glycol for NPG+) so the conventional (EG) antifreeze from yesterday should get along well with it. NPG-R is also noticably thinner than NPG+...this is supposed to help thermal conductivity although it has the same exact specific heat as NPG+ (strange). Lastly NPG-R is not a lifetime coolant like NPG+. It needs to be replaced every two years. Oh and 400F boiling point for NPG-R...like I'll ever need that.

Anyway I went back to the stock 13 psi cap because I don't need 16 psi with the NPG-R (duh). So to testing...99F ambient I recorded 97C solid on the highway (8 miles worth) with the A/C on at 84 MPH. I turned the A/C off and left the highway. While at 54-64 mph for 5 miles I recorded 93-96C. I thought that was AWESOME. Well later in the day I drove when it was 101F and it was 98C with the A/C on at 45-49 MPH. On my way home a few hours later it was 106F and I recorded 104C temps with the A/C on...same 45-49 mph with the occasional stoplight.

In all the above testing I had the fan activation temps cranked up to 115C...so no fans were on unless the A/C was on...and then they were on a lower speed (?medium?).

So 104C...not bad at all for NPG-R. I actually recorded 106C with the 35% conventioanl antifreeze when it was 107F on the way home from work Thursday (*fans on high too*). I'm finally happy with the setup. I may get a vented hood later to loose a few more degrees but that's just gravy.

got a situation for you guys..
yesteday out side temp was in the mid to hi 90's. dont have aftermarkiet water temp guage yet..but stock went to red and add coolant buzzer went off. ( i was parked when all this had happend)( think she was mad at me because i went to test an rx8) newayz..so i waited for an hour.. and added bout 1/2 gallon of water. waited another hour and started her up.no light/ buzzer. temps stayed normal.....drove for about 10 min to autozone to get collant. got 100% anti-freeze. (guy at the counter said since i had added water the mix wouldnt be a good idea. he asked my problem and it old him. he said i should try thermostat. so i also bought thermostat. and upon futher inspection. i noticed my coolant is the color of mud...( i know really bad). so my question to all you gurus
1. what is npg+/-r
2. where can i get the higher preassure rad caps and do they go on the filler neck or the ast.
3. when i install thermostat will i need to bleed system of air
4. to flush coolant can i do it my self or do i need to take it to shop.

i dont think there was any engine damage. (hope not anywayz). i hope i didnt hijack the thread but i figured iwas haveing similar problems.

Yes, you did hijack his thread...
1. Search.
2. The pressure cap goes on the AST. I wouldn't recommend going to a higher pressure cap seeing that your coolant is old; your hoses are probably old as well, which brings the risk of popping one.
3. Yes, you will need to bleed the system because you must remove a bunch of components to get to the housing, which needs to be removed for access.
4. You can do it yourself if you know what you're doing and you don't just let the old coolant run down the street gutter...

Tevor, your temps seem pretty close to what I have seen in my car. So far this summer my car has reached 97C driving hard around town with no A/C. I don't remember my car ever getting past 99C with the A/C on around town. On the way to Sevenstock a couple of years ago my car got up to 106C driving trough Palm Springs up a hill (scared the shit out of me). I think it was like 115 that day :) I have a stock radiator, no foam ducting, distilled water, coolant, and a bottle of Water Wetter. I have a crank pulley and the Greddy underdrive pullies so I don't know if that makes a difference. Let me know if you ever need my car to compare temp differences. It may make an interesting comparo.
Scott

Another thing to consider is a miniature battery. After installing an Oddyssey PC680, I can now see my radiator in the otherwise-stock engine bay. I'll post photos once I finish building a proper tray for it.

-s-

Trevor & fdeeznutz I'd also like to compare temps with you as welll. I live in El Paso, TX and were're getting temps up to 109. On that day my highest temp reading was 96C. Funny thing about my car is that in stop and go traffic it gets cooler, about 89C. On the highway about 94. What I have noticed is I am getting some turbulance from the fans. I feel the fans blowing air through the radiator but I also feel some air being blown back towards the noise of the car while at idle. Both fans are working and spinning in the correct directions. I believe its the air hitting the air box and battery box thats causing the turbulance.

Scott - no higher than 99C with that setup? That's remarkable...about as good as it could possibly get with that combo. As I said before 102C-106C was the norm for me with what should have been a superior setup. My car's on crack...

Man...speed and ambient temp plays a huge role in things. I have the fans set to come on at 106C (pretty much guaranteed I'll be at a stop to see anything over 104C).

Taco Bell drivethru with the A/C on max in 104-105F ambient: 108C (223F) stable (it dropped down to 102C as soon as I got back on the road)

Drive home at 11:30 PM (86F) at 49-54 mph getting on it every now and then: 85-86C (185-187F)

Obviously not a solution for you guys, but I was wondering would putting in a single turbo and eliminating all the stock airbox stuff and relocating the battery help reduce temperatures by creating better flow in the engine bay(less plastic and such) and lower by creating less heat? (one turbo instead of two)
Im really starting to worry and will do just about anything at this point

I have stock motor, stock turbos, stock radiator, stock radiator caps, stock thermostat, stock pulleys, stock everything except for the Miata thermoswitch. I built simple metal fences inside the nose that seal the sides of the radiator opening to the sides of the radiator. I removed the stock plastic air deflectors in the sides of the radiator opening; this makes the inlet larger. I run a coolant mix of 80% water/20% coolant in the summer.

This weekend in 95+ degree weather I towed my fully loaded tire trailer down the highway at 80-85mph for over 4.5 hours each way. Car was also loaded with luggage and a passenger and the a/c was on max the entire time. Coolant temps ran at 185F, rising to 190F if I was following closely behind another car. In stop and go rush hour traffic temps would climb to 195F.

Doing nothing but running a higher ratio of water to coolant will make a nice difference. Sealing the inlet to the radiator makes a huge difference, especially in highway temps.

I've got no undertray, no side sealing, an FMIC, and a stood up Koyo radiator, with greddy pullies, and a B&M Hi-Tek Supercooler (has a Spal fan on it) And in the worst of traffic it will hit 100C then get right back to 94C.... On the highway it runs mid 80 C.... Never touchs 90's unless you start getting on it, and even then it's low 90's.... But we also don't see 100 degree F days in SC....

Damon,

can you post some pictures of your handi-work ?

:-) neil

That's strange. I have koyo, and 2 row FMIC. Daily driving in San Diego my temps would be in 93-95c on the PFC. Whenever I sit in gridlock (everyday) I would turn on the AC and my temps would drop to 87c?? I think you should look into a vented hood. I know it makes a difference.

Just wanted to post my latest change for future reference. I re-wired the fan control circuit to have high speed only...actuated by the PowerFC/datalogit at 97C. So far things have been great. Granted its only been 93-95F lately but if there's not much airflow the coolant hits 97C then the fans crank up and instantly drop the temps down to 93-94C...air on or not...stop and go or not. It doesn't seem to matter. No more trips to 100+C like before.

I dumped the AST BTW...and I'm still runing NPG-R & a 13 psi cap too.

Make the fans come on earlier
 

Why don't you have the fans come on at 86 C? I have set mine to come on at that temp via my datalogit. I lost a motor to coolant seals before and am not taking any chances with cooling.

I usually see temps of 85-86 C or less.
Koyo
Evans
0 psi
Underdrive pullkeys
Fans on at 86 (is this too low???)

fwiw, my fans are set to come on at 86, 87, 89.

I'm running a Koyo with a Greddy FMIC and Evans. In stop/go rush hour traffic in the July, August NY area heat (90 degree high humidity), I would see temps in the high 90s and occasionally would hit 103ish.

Most other times when the car was moving, I'd be in the 86-89 range.

I believe what is killing me is the lack of any ducting due to the FMIC and Radiator setup. When the car is stopped, the fan just pulls the hot air from within the engine compartment back through the radiator. FMIC guys especially ducting sealing the top of the radiator to the nose of the car and along the sides as well. maxcooper did something to this effect. there are some pics in the single turbo section.